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Re: [PATCH v2 1/1] ppc/mmu_helper.c: do not truncate 'ea' in booke206_in

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v2 1/1] ppc/mmu_helper.c: do not truncate 'ea' in booke206_invalidate_ea_tlb()
Date: Wed, 10 Nov 2021 22:00:38 +0100

On Wed, Nov 10, 2021 at 9:25 PM Daniel Henrique Barboza
<danielhb413@gmail.com> wrote:
> 'tlbivax' is implemented by gen_tlbivax_booke206() via
> gen_helper_booke206_tlbivax(). In case the TLB needs to be flushed,
> booke206_invalidate_ea_tlb() is called. All these functions, but
> booke206_invalidate_ea_tlb(), uses a 64-bit effective address 'ea'.
> booke206_invalidate_ea_tlb() uses an uint32_t 'ea' argument that
> truncates the original 'ea' value for apparently no particular reason.
> This function retrieves the tlb pointer by calling booke206_get_tlbm(),
> which also uses a target_ulong address as parameter - in this case, a
> truncated 'ea' address. All the surrounding logic considers the
> effective TLB address as a 64 bit value, aside from the signature of
> booke206_invalidate_ea_tlb().
> Last but not the least, PowerISA 2.07B section [2] makes it
> clear that the effective address "EA" is a 64 bit value.
> Commit 01662f3e5133 introduced this code and no changes were made ever
> since. An user detected a problem with tlbivax [1] stating that this
> address truncation was the cause. This same behavior might be the source
> of several subtle bugs that were never caught.
> For all these reasons, this patch assumes that this address truncation
> is the result of a mistake/oversight of the original commit, and changes
> booke206_invalidate_ea_tlb() 'ea' argument to 'vaddr'.
> [1] https://gitlab.com/qemu-project/qemu/-/issues/52
> [2] https://wiki.raptorcs.com/wiki/File:PowerISA_V2.07B.pdf
> Fixes: 01662f3e5133 ("PPC: Implement e500 (FSL) MMU")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/52
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  target/ppc/mmu_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

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